title: ESR spin trapping for characterization of radical formation in Lactobacillus acidophilus NCFM and Listeria innocua.
abstract: In this study, radicals in pure cultures of Lactobacillus acidophilus NCFM and Listeria innocua were detected in a quantitative way by electron spin resonance spectroscopy using spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) or N-tert-butyl-α-phenylnitrone (PBN). No adverse effect of spin trap addition on viability was observed for any of the bacterial strains. L. acidophilus NCFM had a higher production of radicals than L. innocua when incubated in a growth medium. Furthermore, by using DMPO in a buffer system, the radicals produced by L. acidophilus NCFM could be identified as hydroxyl radicals. The presence of polyethylene glycol, impermeable for bacterial cells, decreased the signal intensity of the ESR spectrum of the DMPO-OH adduct in cultures of L. acidophilus NCFM and indicated quenching of hydroxyl radicals outside the bacteria. This suggests that radical production is an extracellular event for L. acidophilus NCFM.
authors.affiliation: Department of Food Science, University of Copenhagen, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark. abhg@life.ku.dk
authors.forename: Anni B
authors.initials: AB
authors.lastname: Hougaard
authors.forename: Nils
authors.initials: N
authors.lastname: Arneborg
authors.forename: Mogens L
authors.initials: ML
authors.lastname: Andersen
authors.forename: Leif H
authors.initials: LH
authors.lastname: Skibsted
mesh_terms: D019343:Citric Acid; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D007779:Lactobacillus acidophilus / Q000737:chemistry*; D008087:Listeria / Q000378:metabolism*; D050296:Microbial Viability; D010710:Phosphates; D011092:Polyethylene Glycols; D017382:Reactive Oxygen Species / Q000032:analysis* / Q000378:metabolism; D019097:Spin Trapping / Q000379:methods*
chemical_list: D010710:Phosphates; D017382:Reactive Oxygen Species; D019343:Citric Acid; D011092:Polyethylene Glycols
keywords: Free radicals; Listeria; Probiotic bacteria; Viability